This invention relates to polyurethanes and, more particularly, to polyurethane elastomers prepared from polymer/polyols containing high ethylene oxide polyols and to the polyols themselves.
Polyurethane elastomers are used in a wide number of applications, ranging from shoe soles to automobile fascia. In a number of such applications, providing the necessary physical properties requires use of substantial amounts of low molecular weight chain extenders.
Unfortunately, such chain extenders are compatible in only unsatisfactorily low amounts with conventional polypropylene oxide-based polyols, which contain only a minor amount of ethylene oxide, typically as a cap to provide the percentage of primary hydroxyl groups desired, as is known, for the proper reactivity. This incompatibility can be tolerated to some extent, and users typically may add such extenders in amounts up to about 100% or even more by weight or so in excess of the compatible amount. However, the processing problems and limitations created are significant. Thus, bulk shipments and/or storage for even short periods of time is not economically feasible due to the resulting phase separation of the polyol and the chain extender. And, even in use, processing requires appropriate mixing to prevent phase separation. Moreover, the physical properties of the resulting elastomers may sometimes prove unsatisfactory due to, for example, marginal mixing.
Attempts have been made to develop suitable chain extenders that would be compatible in relatively large amounts with such polyols. One technique to enhance the compatibility of chain extenders has been capping polypropylene oxide-based polyols with substantial amounts of ethylene oxide.
The use of such high ethylene oxide capped, propylene oxide-based polyols makes the preparation of polymer/polyols difficult, if not impossible, by presently used techniques. This significantly restricts the utilization of such polyols in elastomer applications because the utilization of polymer/polyols is often needed to allow the preparation of elastomers with satisfactory physical properties, particularly modulus characteristics. The modulus values provided by the polyols themselves are often inadequate.
It is accordingly an object of the present invention to provide highly reactive polymer/polyols which have enhanced compatibility characteristics for low molecular weight chain extenders yet which can be readily prepared.
Another object provides a polymer/polyol-chain extender package which may be stored for extended periods of time without phase separation.
Yet another object lies in the provision of polymer/polyols capable of being converted to elastomers possessing satisfactory physical properties.
A still further object of this invention is to provide elastomers having satisfactory hydrolytic stability.
Yet another object provides polymer/polyols capable of being processed by reaction injection molding techniques with satisfactory and, in some instances, superior demolding characteristics.
Still another object lies in the provision of polyols which can be utilized to prepare polymer/polyols and elastomers having the above-described properties.
Another object of this invention is to provide polyols characterized by self-emulsifying properties when incompatible amounts of certain low molecular weight chain extenders are added.
Other objects and advantages of the present invention will become apparent from the following detailed description.
While the invention is susceptible to various modifications and alternative forms, there will herein be described in detail the preferred embodiments. It is to be understood, however, that it is not intended to limit the invention to the specific forms disclosed. On the contrary, it is intended to cover all modifications and alternative forms falling withing the spirit and scope of the invention as expressed in the appended claims.